Thermochromic paint (another idle musing)

[EBK]

So, a few observations before I conclude my thermochromic experiments as they loosely relate to guitar:
1. Thermochromic pigment cannot replace an LED status indicator on a guitar pedal.  A large (relatively speaking) chunk of aluminum takes too long to get warm and cool down, despite being a good thermal conductor.  This could be due to several factors, including geometry, paint insulation, power, etc.
2.  On that last factor, power, 5W is almost the largest power dissipation I could imagine on a practical, non-tube pedal.  It would still run comfortably off of a One Spot wall wart, for example.  Any more power without more non-visual show and I'd have to consider it simply wasteful, I'm sad to admit.
3.  I could very likely speed up the color change on the heating side of the operation by using a more powerful thermoelectric module (there's that power element, again), but I can't speed up the cool down.  If I reverse the current through the module, the cold side would contact the enclosure, but the hot side would be ferociously heating up the innards, in the same way that a window air conditioner placed in the center of a room can only heat up the room rather than cool it off.
4.  I'm still not done playing around witb this pigment or this thermoelectric module.  I just haven't figured out my next step.   

[Tony Forestiere]

For giggles and grins, toss in a Peltier element.  Both exothermic and endothermic reactions by just reversing the current!  Yeah, expensive and a major power hog, but it should both cool and heat a small section of your painted enclosure rather quickly for a status indicator using a 4PDT.
Thought experiment. 

[EBK]

For giggles and grins, toss in a Peltier element.  Both exothermic and endothermic reactions by just reversing the current!  Yeah, expensive and a major power hog, but it should both cool and heat a small section of your painted enclosure rather quickly for a status indicator using a 4PDT.
Thought experiment. 

My thermoelectric module is a Peltier element.  I just used a more generic name.   

The one I have is only 5W though.  The hot side gets too hot to touch (maybe scalding hot water) and the cold side gets refreshing-beverage cold (I don't think it would freeze a water drop).

I DO appreciate the encouragement to keep experimenting though. 

[Tony Forestiere]

My thermoelectric module is a Peltier element.  I just used a more generic name.   

...The hot side gets too hot to touch (maybe scalding hot water) and the cold side gets refreshing-beverage cold (I don't think it would freeze a water drop).

Got you. It is a shame that there is so much dissimilarity between the hot and cold thermal exchange and dissipation/dispersion to evenly affect a small segment of the paint. Too hot, and not cold enough. Bummer.

4.  I'm still not done playing around with this pigment or this thermoelectric module.  I just haven't figured out my next step.   

That's the frontier spirit! 

[PRR]

> speed up the color change on the heating side ... I can't speed up the cool down.

Thinner metal (Coke-can) would speed both phases.

Hot will be faster than cold until you reduce the heat input so much it barely-warms; even then probably.

No, I don't think it makes a good status indicator. More like: you paint a naked lady on your pedal and she reveals herself over time. I guess the classic is a drinking-glass with a lady in a bikini which turns clear when an iced beverage fills the glass. (I'm probably showing my age.) (Again.)
Not Safe For Work.

[diffeq]

For some artistic use, maybe it could be used in a boost pedal with LM1875 that gets warm in a single spot? like moon through clouds, or light beacon or something.

In any case, cool experiments, Eric!

[EBK]

Thinner metal (Coke-can) would speed both phases.

I'm contemplating cutting a window in an enclosure and securing a small piece of aluminum flashing over said window, perhaps with a gasket of some sort in between. 

With something small and thin enough, it may be worth additional experimenting with the polarity of thermoelectric module and some on/off timing (like a simplified thermostat controller).  This is an academic, non-commercial venture, so I'm not against putting a ton of extra parts into this idea in order to explore more possibilities.

[EBK]

There are a couple of artistic applications I've been thinking about for this black/white color change.  For instance, for a long time, I've wanted to make a Spy vs. Spy themed pedal.

[duck_arse]

paint an incandescent light bulb.

[EBK]

paint an incandescent light bulb.

https://vimeo.com/2616647/description

[Tony Forestiere]

...More like: you paint a naked lady on your pedal and she reveals herself over time. I guess the classic is a drinking-glass with a lady in a bikini which turns clear when an iced beverage fills the glass. (I'm probably showing my age.) (Again.)

My paternal "Grandpa" had a set of glasses like those. He also had a couple of decks of playing cards with similar artwork for when the boys came over to play Pinochle and Poker. "Grandma" didn't seem to mind them. I guess back then, folks didn't get their panties in a wad over the depiction of attractive nude women in, what I would call, a tasteful form. Look at some of the nose art that adorned The U.S. WWII bombers. Stunning Americana. http://worldwartwo.filminspector.com/2014/07/nose-art.html
Times were simpler without loud, insufferable people screaming that they are offended by something, nothing, or everything.
(Sorry to interject and derail.  )

I saw the video of the painted light-bulb array. Only allowed for the heating, but not cooling of the painted surface. Neat idea, but I see the guy recorded at 5x. Very slow. How many Peltiers do you want to play with? How much PS current can you supply? Paint a large sheet of metal/glass in a grid pattern with several different shades of paint, stick an element to each, program something to heat/cool each grid individually in a random pattern, and sell it as a piece of expensive art! 

[EBK]

My next experiments will likely involve measuring heating and cooling times for a business-card-sized piece of aluminum flashing.  I'm hoping it can be done in mere seconds rather than minutes.

[amptramp]

You could put the Peltier element on the outside of the enclosure and put the thermochromic paint on the Peltier element itself.  That should get the maximum heating and cooling speed.  The back of the element could be thermally connected to the enclosure.

You could get some interesting results with a Fuzz Face where changing the box temperature would change the characteristics.  Or you could use the Peltier device to stabilize the characteristics of the Fuzz Face.